London marathon kicks off with a moment of silence

Runners observe a moment of silence before the start of the London Marathon in Greenwich, southeast London, on April 21.

Undaunted by the Boston Marathon bombings, big crowds lined the route of the London Marathon on Sunday to cheer on some 36,000 runners who paid their respects to the Boston victims by wearing black ribbons and holding a 30-second silence before the start.

Jason Darnall of Kentucky, who ran the Boston Marathon in 2012 and chose to compete in London's marathon on Sunday, wears a black ribbon at the start of the mass race in Greenwich Park, southeast London.

Chris Jackson / Getty Images

Priscah Jeptoo of Kenya runs down the Mall towards finish line and victory in the Women's Elite section during the London Marathon on Sunday.

Matt Dunham / AP

Lulu, a member of a British police explosive dog search team, patrols during the London Marathon on Sunday.